In recent years, various adhesive patches and adhesive preparations have been developed. Adhesive patch and adhesive preparation are highly superior from the aspects of wound protection and/or continuous transdermal administration of a drug.
In general, an adhesive patch comprises a support made of a cloth, a plastic film and the like and an adhesive layer laminated on the support, and is generally provided with a release liner laminated on the adhesive layer and in a package made of a resin film and the like.
In such adhesive patch, when the adhesive layer becomes thick, the edge of the adhesive patch is easily rubbed against clothes and the like and turned up, as well as the components of the adhesive layer protrude from the edge of the adhesive patch, i.e., cold flow, thus posing problems during adhesion to the skin.
Cold flow occurs depending on the property of an adhesive. It often occurs when, in particular, an adhesive patch is under a load for a long time, namely, when an adhesive patch is contained in a package and stored for a long period and the like.
Adverse influences of cold flow include, for example, degraded performance of taking out of an adhesive patch from a package, which is caused by adhesion of protruded adhesive layer components to the inside of the package, edge lifting and staining of adhesive patch during adhesion to the skin, a lower effect including a lower medicinal effect of the adhesive patch and the like. Therefore, an adhesive patch desirably has an edge which is not easily rubbed against clothes and does not permit easy cold flow, and has an adhesive layer retaining the original shape.
To balance prevention of skin irritation (improvement of moisture permeability) and improvement of transdermal absorbability of the drug, which are contradictory for an adhesive preparation containing a transdermally absorbable drug, JP-A-9-124462 discloses an adhesive patch and an adhesive preparation that achieve the balance thereof by disposing a void forming member such as a non-woven fabric and the like in an adhesive layer to form voids in the adhesive layer.
However, the voids formed in the adhesive layer described in JP-A-9-124462 are sequentially present in the flat plane direction of the adhesive patch and reach the edge of the adhesive patch, and therefore, adhesive layer components such as additives and the like may be affected by the environment outside the adhesive patch via the voids. In the adhesive patch described in patent document 1, therefore, a new consideration to suppress volatilization and decomposition of adhesive layer components and improve stability of the adhesive layer components over time is necessary.
In addition, the constitution disclosed in JP-A-9-124462, wherein voids are sequentially present in the flat plane direction of the adhesive patch and reach the edge of the adhesive patch, aims to balance improvement of moisture permeability and improvement of transdermal absorbability of drug, and therefore, is not effective for the prevention of the aforementioned cold flow. The constitution disclosed in JP-A-9-124462 is still associated with the possible problems mentioned above, i.e., protrusion of adhesive layer components from the edge of an adhesive patch, which is particularly frequently observed during long-term preservation of an adhesive patch under a load for a long time and the like, degraded take out performance of an adhesive patch from a package due to adhesion of protruded adhesive layer components to the inside of the package, edge lifting of an adhesive patch during adhesion to the skin and the like.